Riverbed Elevations and Water Quality

of the Missouri River at Sioux City,

Iowa, 2002-03

Scientific Investigations Report 2004-5079

Prepared in cooperation with the CITY OF SIOUX CITY

U.S. Department of the Interior

U.S. Geological Survey
Riverbed Elevations and Water Quality 

of the Missouri River at Sioux City, 

Iowa, 2002-03

By Daniel E. Christiansen

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the City of Sioux City

Scientific Investigations Report 2004-5079
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

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Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report.

Suggested citation:

Christiansen, D.E., 2004, Riverbed elevations and water quality of the Missouri River at Sioux City, Iowa, 2002-03: 

U.S. Geological Survey Scientific Investigations Report 2004-5079, 14 p.
 iii

Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Purpose and Scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Description of Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Data-Collection Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Riverbed-Elevation Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Water-Quality Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Quality Assurance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Riverbed Elevation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Water Quality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figures

1. Map showing location of Sioux City study area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

2. Map showing location of data-collection sites on Missouri River,

Sioux City, Iowa. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

3. Cross-section A’–A located at Sioux City municipal well field . . . . . . . . . . . . . . . . . . . . . . . . . .5

4–6. Upstream/downstream traverses:

4. Upstream/downstream traverse on the right bank (Nebraska) . . . . . . . . . . . . . . . . . . . .6

5. Upstream/downstream traverse on the mid channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

6. Upstream/downstream traverse on the left bank (Iowa) . . . . . . . . . . . . . . . . . . . . . . . . . .8

Tables

1. Physical properties determined in samples from the Missouri River at

Sioux City, Iowa, 2002-2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

2. Major ion concentrations in samples from Missouri River at

Sioux City, Iowa, 2002-2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

3. Nutrient, concentrations in samples from Missouri River at

Sioux City, Iowa, 2002-2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

4. Selected dissolved pesticides in samples from Missouri River at Sioux City,

Iowa, 2002-2003. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

5. Pesticide constituents not detected in surface-water samples from Missouri River

at Sioux City, Iowa, 2002-2003 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
iv 

Conversion Factors, Abbreviations, Vertical and 

Horizontal Datum

Abbreviated water-quality units used in this report: Chemical concentrations are reported in 

milligrams per liter (mg/L) and micrograms per liter (μg/L). A milligram per liter expresses the 

concentration of chemical constituents in solution as weight (milligrams) of solute per unit 

volume (liter) of water. A microgram per liter expresses the concentration of chemical constituents in solution as weight (micrograms) of solute per unit volume (liter) of water. Microsiemens 

per centimeter (μS/cm) at 25 degrees Celsius (°C) expresses the capability of a unit volume of 

water to conduct an applied electrical current.

Vertical Datum: Vertical coordinate information is referenced to the National Geodetic Vertical 

Datum of 1929 (NGVD of 29). Elevation as used in this report, refers to distance above or below 

NGVD of 29. NGVD of 29 can be converted to the North America Vertical Datum of 1988 (NAVD of 

88) by using the National Geodetic Survey conversion utility available at URL 

http://www.ngs.noaa.gov/TOOLS/Vertcon/vertcon.html

Horizontal datum: Horizontal datum information is referenced to the North American Datum of 

1983 (NAD of 83).

Multiply By To obtain

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

cubic foot per second (ft3/s) 0.02832 cubic meter per second

gallon per minute (gal/min) 0.06309 liter per second

million gallons per day (Mgal/d) 0.04381 cubic meter per second
Riverbed Elevations and Water Quality

of the Missouri River at Sioux City,

Iowa, 2002-03

By Daniel E. Christiansen

Abstract

The U.S. Geological Survey, in cooperation with the City 

of Sioux City, Iowa, conducted an investigation of the Missouri 

River, during 2002-2003, to assess changes in riverbed elevations from its confluence with the Big Sioux River, downstream 

to the area of the Sioux City municipal well field. Water-quality 

samples also were collected across the Missouri River to 

provide additional information on the differences between the 

water quality of the Missouri River and Big Sioux River in the 

well field area. 

The water supply at Sioux City, Iowa, is withdrawn from 

fourteen vertical wells and one horizontal collector well. 

Twelve vertical wells and the collector well are completed in 

the alluvial sand and gravel aquifer adjacent to the Missouri 

River at Sioux City. The well field is located on the left bank 

(looking downstream) of the Missouri River about 0.5 mile 

upstream from USGS streamflow gage 06486000, and approximately 5,000 feet downstream from the confluence with the 

Big Sioux River.

The Missouri River, adjacent to the Sioux City alluvial 

well field, consists of the combined streamflows from the 

Missouri and the Big Sioux Rivers. The streamflows do not 

appear to be well mixed downstream from the confluence, and 

the streamflow directly adjacent to the well field could be predominately from the Big Sioux River. The U.S. Geological 

Survey measures streamflow on the Missouri River at Sioux 

City, Iowa (USGS streamflow gage 06486000). The riverbed of 

the Missouri River at Sioux City consists of a sequence of sands 

and gravels. The surface of the riverbed is undulatory, with continuously migrating riverbed forms, 5 to 8 feet in relief, of sand 

and gravel.

Measurements of riverbed elevations from October 1, 

2002, to September 30, 2003, showed an annual change of as 

much as 8 feet with the majority of the riverbed change closer 

to 5 feet. The largest change occurred near a wing dike on the 

Nebraska side of the Missouri River. On the Iowa side, the 

annual change was close to 5 feet. The results showed that 

channel fill occurred in the winter months and scour occurred 

during the summer months.

Results of analyses of water samples collected at five locations across the Missouri River, near the municipal well field, 

were similar for most samples. Higher values of specific conductance and turbidity were recorded on the Iowa side of the 

Missouri River, the side from which the Big Sioux River enters 

upstream. Higher concentrations of chloride, ammonia nitrogen, nitrate nitrogen, and atrazine also were detected on the 

Iowa side of the Missouri River. Based on these results, there 

does not appear to be complete mixing of water from the 

Missouri and Big Sioux Rivers near the municipal well field.

Introduction

The City of Sioux City, Iowa, obtains part of its municipal 

water supply from the alluvial sand and gravel aquifer along 

the Missouri River (fig. 1). The well field consists of fourteen 

vertical wells, ranging in depth from 90 to 134 ft and one horizontal collector well 85 ft deep, located on the left bank of the 

Missouri River, completed in the alluvial aquifer (Iowa Department of Natural Resources, 2001) (fig. 2). The alluvial aquifer 

consists of sand and gravel deposits of glacial and fluvial origin 

(Prior, 1991).

Because of the proximity of the Sioux City municipal well 

field to the Missouri River, river-borne contaminants have the 

potential to affect the water quality of the municipal supply, 

both chemically and biologically. Ground-water gradients can 

be from the riverbed to the alluvial aquifer during times of well 

withdrawals, inducing flow from the river to the well field. 

Alluvial aquifer material of suitable thickness may function as 

an efficient filter of river-borne particulate material and mitigate the chemical effects of the river water. Information on the 

thickness of the alluvial aquifer material between the riverbed 

and municipal well intakes is needed, particularly if changes in 

this thickness occurs. Horizontal collector wells are constructed 

by installing laterals in the aquifer beneath or adjacent to the 

riverbed; and therefore, collector-well laterals would be most 

susceptible to changes in the thickness and filtration effectiveness of aquifer material. Additionally, if the municipal wells 

induce flow only from adjacent river bank areas and the river 

streamflow is not well mixed, then understanding the source of 

the induced recharge is needed to develop appropriate sourcewater protection programs.
2 Riverbed Elevations and Water Quality of the Missouri River at Sioux City, Iowa, 2002-03

Figure 1. Location of Sioux City study area. Big

Missouri

Illinois

Wisconsin

South Minnesota

Dakota

Nebraska

IOWA

Woodbury Woodbury

County

Woodbury

County

Index Map

Floyd River

Study Area

Sioux City

Sioux River

Mississippi River

Missouri

River

Missouri

River

MILES

KILOMETERS

0

0

6

2 4 6

2 4

42o30’

96o25’

96o10’ 95o55’

42o20’

Woodbury County Woodbury County oodbury County

Base from U.S. Geological Survey digital data, 1:100,000, 1991

Universal Transerse Mercator projection

Zone 15

To help address concerns about protection of the municipal water supply from river-borne contaminants, the U.S. 

Geological Survey (USGS), in cooperation with the City of 

Sioux City, conducted a study of the Missouri River from 2002 

to 2003, to provide information about the annual changes in 

riverbed elevations and water quality. The study focused on 

whether the Big Sioux River affects water quality at the riverbank area adjacent to the alluvial well field located about 

5,000 ft downstream from the confluence of the Big Sioux 

River with the Missouri River. 

The objectives of the study were to: 1) provide bathymetry data 

on changes in riverbed elevation, both across and along upstream/downstream traverses of the Missouri River, in the area 

of the Sioux City well field and 2) collect samples of selected 

water-quality constituents to determine the differences in water 

quality across the Missouri River in the well field area.
Figure 2. Location of data-collection sites in study area on Missouri River, Sioux City, Iowa. 

Big Sioux River

Collector Well Collector Well

South South 

Sioux City Sioux City

Collector Well

South 

Sioux City

WingDikesWingDikes

NEBRASKA

A

A'

00

0.25 

Base from U.S. Geological Survey, Sioux City South, 1:24,000, 1993Universal Transerse Mercator projectionZone 15

EXPLANATION

Upstream/downstream bathymetric traverseCross sectionSioux City municipal wellsUpstream discharge measurment location

A‘ A
4 Riverbed Elevations and Water Quality of the Missouri River at Sioux City, Iowa, 2002-03

Purpose and Scope

This report describes results of the study of changes in 

riverbed elevation and water quality of the Missouri River in the 

Sioux City study area. Hydrologic and water-quality data were 

collected from October 2002 through September 2003 along the 

Missouri River near Sioux City’s municipal well field (fig. 2). 

Hydrologic data collected consisted of twenty-four measurements along section A’–A of the Missouri River and quarterly 

measurements along three upstream/downstream traverses 

(fig. 2). Water-quality data were collected December 3, 2002, 

March 19, 2003, and June 25, 2003.

Information from this study will contribute to understanding the characterization of the Missouri River riverbed 

changes and the mixing of the streamflow below the confluence 

of the Missouri and Big Sioux Rivers near Sioux City. The 

hydrologic data from the Missouri River will furnish results 

needed by managers for planning and operation of public-water 

supply collection and treatment facilities, and provide information that is relevant to present and/or future public-water 

supplies utilizing alluvial-aquifer sources.

Description of Study Area

Sioux City, Iowa, is located in western Woodbury County, 

Iowa on the left bank of the Missouri River in northwest Iowa 

(fig. 1). The city extends east from the Missouri Alluvial Plain 

into the Loess Hills landform region (Prior, 1991). The topography of these two landform regions differs significantly; the 

Missouri Alluvial Plain is nearly level, with low relief ridges 

and swales that mark former positions of the river. The topography of the Loess Hills is sharp featured; with alternating peaks 

and saddles that trend along narrow, non-linear ridge crests 

(Prior, 1991). The boundary between the Missouri Alluvial 

Plain and the Loess Hills landform regions is abrupt. 

The study area contains the Sioux City municipal water 

supply well field which is located about 0.5 mile upstream 

from the USGS streamflow gage 06486000 and approximately 

5,000 ft downstream from the Missouri and Big Sioux Rivers 

confluence. Annual mean daily streamflow at this site is about 

26,640 ft3/s (October 2000 through September 2001)1. The 

land-surface elevation of the river valley in the study area varies 

from about 1,090 to 1,100 ft, and to the east, in the Loess Hills, 

the uplands rise to an elevation above 1,200 ft in some areas. 

Upstream from the study area, Missouri River streamflow is 

controlled by six mainstem dams constructed by the U.S. Army 

Corps of Engineers from 1940 to 1964. The Gavins Point Dam 

upstream from Sioux City controls the discharge of the 

Missouri River at Sioux City. Numerous wing dikes and other 

control structures also have been constructed to stabilize the 

navigation channel in the vicinity of Sioux City.

Acknowledgments

The author thanks the City of Sioux City Water Department staff for their assistance in gathering technical information. The author also thanks Kent Becher, Jim Caldwell, Joe 

Gorman, Rich Kopish, Matt Noon, Doug Schnoebelen, and 

James Sondag, USGS, for assisting with data collection and 

compilation.

Data-Collection Methods

Data-collection included riverbed elevation along one 

cross section and three upstream/downstream traverses. 

Quality-assurance procedures in the field included at least four 

transects for the riverbed-elevation data measurements and two 

sets of blanks for the water-quality data.

Riverbed-Elevation Data

Bathymetric data were collected from October 1, 2002, to 

September 30, 2003, on the Missouri River near the Sioux City 

municipal well field. The data consisted of 24 measurements at 

cross-section A’–A along with quarterly measurements of midchannel, left-channel (Iowa), and right-channel (Nebraska) 

8,500 ft upstream/downstream traverses (fig. 2). The bathymetric data were collected using a Bathy Pro 500® echo 

sounder (BPES) with a three-degree transducer. The sounder, 

which has a higher resolution and lower sensitivity to suspended sediment than the Acoustic Doppler Current Profiler 

(ADCP), was used due to the generally high suspendedsediment content of the Missouri River. Streamflow-discharge 

measurements were collected using an ADCP and completing 

four transects (two in each direction) under steady-flow conditions (Lipscomb, 1995). A Global Positioning Systems (GPS) 

receiver is integrated into the BPES and ADCP units to provide 

accurate position measurements. Individual cross-section measurements were then graphically merged to produce figures 3-6 

showing the range of measured riverbed elevation change and 

measured water-surface elevation during the data-collection 

period. The elevations of the collector-well laterals below the 

riverbed also are shown for reference (figs. 3-6). 

Water-Quality Data

Discrete water-quality samples were collected at five regularly spaced locations across the Missouri River at crosssection A’–A near the municipal well field (fig. 2). The distance between the sampling points was approximately 100 ft, 

depending on the width of the river at the time of sampling. 

Discharge measurements at cross-section A’–A and an 

upstream discharge measurement were made on the Missouri 

River using the ADCP each time water-quality samples were 

collected. The upstream discharge measurement allowed the 

1

Real-time stage and discharge data for this stream-gaging station

can be accessed through the Internet at URL

http://webdiaiwc.cr.usgs.gov/data.html
Data-Collection Methods 5

comparison of the discharge contribution of the Big Sioux 

River to that of the Missouri River at cross-section A’–A to be 

determined by subtracting the discharge at cross-section A’–A 

from the upstream discharge.

Water-quality samples from the Missouri River were collected on December 3, 2002, during low-flow conditions, on 

March 19, 2003, following snowmelt, and on June 25, 2003, 

following a spring/summer precipitation event. The samples 

were collected using the isokinetic, depth-integrated, equalwidth-increment (EWI) sampling method (U.S. Geological 

Survey, 1998). EWI is used frequently on streams that are sand 

riverbeds; the dominant Missouri River riverbed sediment is 

sand. Samples were analyzed in the field at the time of sample 

collection for dissolved oxygen, pH, specific conductance, and 

temperature (U.S. Geological Survey, 1998). Laboratory analyses consisted of major ions, nutrients, pesticides, and physical 

properties (Fishman, 1993; Zaugg and others, 1995). Laboratory analyses were performed at the USGS National Water 

Quality Laboratory in Lakewood, Colorado.

Quality Assurance

Discharge measurements were collected using the ADCP. 

To ensure quality of data collected with the ADCP, all USGS 

standard procedures were followed as prescribed in Lipscomb 

(1995).

Water-quality measurements followed collection procedures outlined in U.S Geological Survey National field manual 

for the collection of water-quality data, (U.S. Geological 

Survey, 1998). Two field blanks were collected for water-quality quality-assurance purposes. Both blanks had no detections 

for all constituents sampled indicating quality-assurance procedures were appropriate for the study. 

Figure 3. Cross-section A’–A located at Sioux City municipal well field.

Observed range of water-surface elevation 

Observed range of riverbed elevation 

First tier of collector well

Second tier of collector well

DISTANCE FROM IOWA (LEFT BANK) TO NEBRASKA (RIGHT BANK), IN FEET

ELEVATION ABOVE NGVD 29, IN FEET

0 100 200 300 400 500 600

1,080

1,070

1,060

1,050

1,040

1,030

1,020

1,010

1,000

IOWA NEBRASKA

A' A
6 Riverbed Elevations and Water Quality of the Missouri River at Sioux City, Iowa, 2002-03

Riverbed Elevation

An annual change in riverbed elevation of as much as 8 ft 

was observed, with most of the range being less than 5 ft of 

change at the A’–A cross-section location near the municipal 

water supply (fig. 3). The deepest riverbed elevation measured 

was about 1,040 ft. This deep location was on the right-bank 

(Nebraska) side of the river, probably due to streamflowinduced scour behind the wing dike located at the site. The 

riverbed at an elevation of 1,040 ft is over 20 ft higher than the 

depth of the shallowest collector well lateral. The lowest riverbed elevation measured on the left bank (Iowa side) was 

1,053 ft, which is greater than 30 ft above the elevation of the 

shallowest collector-well lateral. 

The right-bank (Nebraska Side) traverses show variable 

riverbed elevations caused by scour (fig.4). The wing dikes 

along the right bank that can be seen in figure 2 probably cause 

this scour. The wing dikes in certain locations caused scour to 

within 5 ft of the depth of the collector-well laterals on the Iowa 

side of the Missouri River, although considerably upstream 

from the well-field area. The deepest riverbed elevation 

measured on the mid-channel traverse was 1,052 ft, about 33 ft 

above the shallowest collector-well lateral (fig. 5). The midchannel traverse had a maximum change of 11 ft, with the range 

typically 7 ft or less. The deepest riverbed elevation measured 

on the left-bank (Iowa side) traverse was approximately 

1,047 ft, about 27 ft above the elevation of the shallowest 

collector-well lateral (fig. 6), but located upstream from the 

well field area.

Water Quality

The Missouri and Big Sioux Rivers discharge measurements showed that the majority of the streamflow is contributed 

by the Missouri River. The Big Sioux River’s largest proportion 

of the combined stream flow at cross-section A’–A was just 

over 14 percent on December 3, 2002, and the smallest proportion was 7 percent of the combined streamflow on June 25, 

2003. During the winter, the Big Sioux River has a slightly 

larger proportion of streamflow passing the municipal well field 

than during the larger streamflows of the summer.

Figure 4. Upstream/downstream traverse on the right bank (Nebraska).

Observed range of water-surface elevation 

Observed range of riverbed elevation 

First tier of collector-well laterals

Approximate location of A-A’ cross section

Second tier of collector-well laterals

LENGTH OF TRAVERSE, IN FEET

ELEVATION ABOVE NGVD 29, IN FEET

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000

1,080

1,070

1,060

1,050

1,040

1,030

1,020

1,010

1,000

Upstream Upstream and downstream right bank (Nebraska) traverse Downstream
Water Quality 7

The physical-properties data of Missouri River water 

samples are presented in table 1. Water temperature and pH 

values were consistent for each sampling date and location. 

There were seasonal changes measured in specific conductance, 

turbidity, and total dissolved solids (TDS) in all samples. 

Factors affecting turbidity in surface water include the physical 

properties of the surficial materials within the drainage basin, 

anthropogenic factors, land use, season, river stage, and 

discharge (American Society for Testing Materials, 1969).

During low-flow conditions (December 3, 2002), turbidity 

values of samples collected at all five sampling locations were 

low. Turbidity in water is due to the presence of suspended and 

dissolved solids and colloidal materials of various origins 

(IHO-WHO, 1978). The low turbidity values from samples 

collected in December 2002 are interpreted to be the absence of 

suspended solids, due to lack of surface runoff, and minimal 

amounts of algae and other microorganisms. 

An increase in turbidity after snowmelt on March 19, 

2003, was observed at the left bank and left-mid channel sample locations, which correlate with the side that water from the 

Big Sioux River enters the Missouri River. The increase in 

turbidity is attributed to a rise in river stage due to snowmelt, 

surface runoff, and the resulting increase in suspended 

sediment. 

The turbidity in samples collected on June 25, 2003, was 

the highest in samples collected from the center channel to the 

right bank and lowest in samples collected from the left bank. 

During the summer months, water is released from upstream 

dams along the Missouri River. The increase in turbidity in the 

Missouri River at the sampling locations is attributed to the 

increase in stage and discharge from releases and from runoff 

following precipitation events and resulting increase in suspended sediment. Turbidity in surface water is generally larger 

in summer months due to an increase in suspended and dissolved mineral and organic material as shown by USGS streamflow gage 06610000 Missouri River at Omaha, NE (Nalley and 

others, 2001). The heterogeneity of turbidity observed in samples collected at this sampling point indicates that water in the 

Missouri River is not well mixed about 5,000 ft downstream 

from its confluence with the Big Sioux River. 

Figure 5. Upstream/downstream traverse on the mid channel.

Observed range of water-surface elevation 

Observed range of riverbed elevation 

First tier of collector-well laterals

Approximate location of A-A’ cross section

Second tier of collector-well laterals

LENGTH OF TRAVERSE, IN FEET

ELEVATION ABOVE NGVD 29, IN FEET

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000

1,080

1,070

1,060

1,050

1,040

1,030

1,020

1,010

1,000

Upstream Upstream and downstream mid-channel traverse Downstream
8 Riverbed Elevations and Water Quality of the Missouri River at Sioux City, Iowa, 2002-03

Specific conductance was larger in samples from the left 

bank and left-mid channel than from the mid channel to right 

bank. Chemical analyses show that samples from the left side of 

the Missouri River have larger concentrations of dissolved ions 

compared to samples from the right side, which indicates that 

the water on the left side of the Missouri River is affected by 

discharge from the Big Sioux River. Specific conductance and 

TDS were the highest during the December 2003 samples, 

probably reflecting ground-water discharges during low-flow 

conditions or lack of dilution from runoff.

Concentrations of calcium, magnesium, sodium, potassium, chloride, sulfate, fluoride, silica, iron, and manganese 

vary in samples collected at each sampling location as well as 

seasonally (table 2). Sulfate was present in all samples with 

concentrations ranging from 141 to 211 mg/L. Chloride concentrations were larger in samples collected on the left bank of the 

river compared to the mid channel and along the right bank of 

the river in all samples. The largest concentration of chloride, 

23 mg/L, was detected in the March 19, 2003, left-bank sample. 

This may indicate that the possible sources of chloride in the 

Missouri River are from the Big Sioux River. Sources of chloride in streamflow can include human or animal waste, or 

deicing agents used on roadways (IHD-WHO, 1978; U.S. 

Environmental Protection Agency, 1995).

Ammonia nitrogen, nitrite plus nitrate, phosphorus, and 

ortho-phosphorus were present in all samples collected during 

at least one of the collection dates (table 3). Measured concentrations of ammonia nitrogen were between 0.02 mg/L and 

0.50 mg/L. Ammonia nitrogen had a larger concentration in the 

March 19, 2003, collection date in samples collected along the 

left bank of the river. Ammonia nitrogen also was slightly larger 

on March 19, 2003, and June 25, 2003, in the left-bank samples 

compared to the right-bank samples. The presence of ammonia 

in water can be the result of decomposition of wastes, and from 

agricultural runoff. Concentrations of nitrite plus nitrate nitrogen were composed primarily of nitrate nitrogen, and were 

detected in all samples. No sample exceeded the U.S. Environmental Protection Agency (USEPA) maximum contaminant 

level for nitrate (10 mg/L as N) (U.S. Environmental Protection 

Agency, 1996). Samples collected along the left bank of the 

river had larger concentrations of nitrate nitrogen compared to 

the samples on the right bank in all samples collected in 2002-

2003. This also is evidence of Big Sioux and Missouri River 

waters not being well mixed.

Figure 6. Upstream/downstream traverse on the left bank (Iowa).

Observed range of water-surface elevation 

Observed range of riverbed elevation 

First tier of collector-well laterals

Approximate location of A-A’ cross section

Second tier of collector-well laterals

LENGTH OF TRAVERSE, IN FEET

ELEVATION ABOVE NGVD 29, IN FEET

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000

1,080

1,070

1,060

1,050

1,040

1,030

1,020

1,010

1,000

Upstream Upstream and downstream left bank (Iowa) traverse Downstream
Table 1. Physical properties determined in samples from the Missouri River at Sioux City, Iowa, 2002-2003.[M/D/YY, month/day/year; ft3/s, cubic feet per second, mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg C, degrees Celsius; NTU, nep--, no data available]

Date

(M/D/YY) Time

Missouri River

discharge

at 06486000

(ft3/s)

Big Sioux River

discharge

(ft3/s)

Oxygen,

dissolved

(mg/L)

pH water whole 

field

(standard units)

Specific 

conductance 

(μS/cm)

Temperature 

water

(deg C)

Turbi

(NT

Left bank (Iowa)

12/3/2002 15:10 14,300 2,100 13.7 8.4 836 1.0 113/19/2003 11:25 24,000 3,158 10.7 8.2 673 4.5 716/25/2003 11:45 34,700 2,465 5.9 8.0 701 24.0 603

Left-mid channel

12/3/2002 15:05 14,300 2,100 13.6 8.4 832 1.0 113/19/2003 11:35 24,000 3,158 11.5 8.4 724 5.0 246/25/2003 12:25 34,700 2,465 6.8 8.1 671 23.5 798

Mid channel

12/3/2002 15:00 14,300 2,100 13.6 8.5 813 1.0 103/19/2003 11:40 24,000 3,158 11.8 8.4 739 5.5 146/25/2003 12:30 34,700 2,465 6.7 8.1 662 23.5 915

Right-mid channel

12/3/2002 14:55 14,300 2,100 13.5 8.5 803 1.0 113/19/2003 11:50 24,000 3,158 11.8 8.4 733 5.5 126/25/2003 12:45 34,700 2,465 6.9 8.1 656 23.5 873

Right bank (Nebraska)

12/3/2002 14:50 14,300 2,100 13.4 8.5 804 1.0 123/19/2003 11:55 24,000 3,158 11.8 8.4 735 5.5 166/25/2003 12:50 34,700 2,465 6.8 8.1 654 23.5 876
Table 2. Major ion concentrations in samples from Missouri River at Sioux City, Iowa, 2002-2003.[M/D/YY, month/day/year; mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than]

Date

(M/D/YY) Time

Hardness

(mg/L as

CaCO3)

Calcium

(mg/L

as Ca)

Magnesium

(mg/L 

as Mg)

Sodium

(mg/L

as Na

Potassium 

(mg/L

as K)

Chloride

(mg/L

 as CL)

Sulfate

(mg/L

 as SO4)

Fluoride

(mg/L

 as F)

Silica

(mg/L

 as SiO2)

Left bank (Iowa)

12/3/2002 15:10 270 64 26 68 5.2 14 211 0.56 7.1 3/19/2003 11:25 230 59 21 46 7.9 23 141 0.40 9.5 6/25/2003 11:45 240 56 24 51 6.0 14 162 0.50 8.0 

Left-mid channel

12/3/2002 15:05 280 66 26 66 4.5 13 210 0.50 7.4 3/19/2003 11:35 240 61 22 57 5.7 12 176 0.51 10 6/25/2003 12:25 210 51 19 58 6.1 9.8 163 0.51 7.6 

Mid channel

12/3/2002 15:00 270 64 26 69 4.7 11 210 0.56 7.4 3/19/2003 11:40 250 62 23 62 4.9 9.2 189 0.51 11 6/25/2003 12:30 200 51 18 57 6.2 9.4 161 0.51 7.6 

Right-mid channel

12/3/2002 14:55 260 61 25 72 4.6 10 209 0.53 7.4 3/19/2003 11:50 240 60 23 64 5.2 9.0 185 0.50 11 6/25/2003 12:45 200 50 18 56 6.2 9.4 159 0.50 7.6 

Right bank (Nebraska)

12/3/2002 14:50 240 57 23 69 5.0 10 208 0.57 7.0 3/19/2003 11:55 240 61 22 62 5.0 9.4 186 0.48 11 6/25/2003 12:50 200 51 18 56 6.2 9.4 159 0.50 7.5 
Table 3. Nutrient, concentrations in samples from Missouri River at Sioux City, Iowa, 2002-2003.[M/D/YY, month/day/year; mg/L, milligrams per liter; <, less than]

Date

(M/D/YY) Time

Nitrogen, 

ammonia

dissolved

(mg/L as A)

Nitrogen,

nitrite

dissolved

(mg/L as N)

Nitrogen,

ammonia + 

organic

dissolved

(mg/L as N)

Nitrogen,

NO2+NO3

dissolved

(mg/L as N)

Nitrogen,

ammonia + 

organic total

(mg/L as N)

Phosphorus,

total

(mg/L)

Phosp

diss

(mg/L 

Left bank (Iowa)

12/3/2002 15:10 0.03 0.01 0.24 0.53 0.39 0.05 03/19/2003 11:25 0.50 0.06 1.4 1.5 1.8 0.54 06/25/2003 11:45 0.13 0.02 0.57 1.2 3.2 1.0 0

Left-mid channel

12/3/2002 15:05 0.03 0.01 0.22 0.49 0.39 0.05 03/19/2003 11:35 0.13 0.02 0.43 0.54 0.68 0.16 06/25/2003 12:25 0.06 0.02 0.35 0.35 3.9 1.4 0

Mid channel

12/3/2002 15:00 0.02 0.00 0.23 0.31 0.34 0.04 03/19/2003 11:40 0.03 <0.01 0.24 0.24 0.40 0.07 06/25/2003 12:30 0.06 0.02 0.33 0.35 4.1 1.4 0

Right-mid channel

12/3/2002 14:55 0.02 <0.01 0.22 0.12 0.29 0.03 03/19/2003 11:50 0.03 <0.01 0.22 0.25 0.41 0.08 06/25/2003 12:45 0.06 0.02 0.38 0.38 4.1 1.4 0

Right bank (Nebraska

12/3/2002 14:50 <0.04 <0.01 0.19 0.12 0.29 0.03 03/19/2003 11:55 0.03 <0.01 0.24 0.26 0.45 0.09 06/25/2003 12:50 0.06 0.02 0.41 0.37 4.2 1.4 0
12 Riverbed Elevations and Water Quality of the Missouri River at Sioux City, Iowa, 2002-03

Pesticide samples were collected for analysis at the leftand right-bank locations along cross-section A’–A. Analytical 

results of all pesticides that had at least one detection on a specific sample date are listed in table 4, and pesticides that had no 

detection are listed in table 5. Atrazine and deethylatrazine were 

detected on all sample dates in all samples. Deethlyatrazine was 

detected by the laboratory on 5 out of 6 samples, but at a low 

concentration (<0.08 μg/L). The presence of deethylatrazine 

would be expected because it is a degredate of atrazine. The 

concentrations of atrazine were the largest in samples on the left 

bank of the river, but still were below the drinking-water regulation of 3 μg/L set by the USEPA (U.S. Environmental Protection Agency, 1996). The larger concentrations occurred in the 

March 19, 2003, and June 25, 2003, samples, which could indicate snowmelt runoff in the spring and agricultural runoff in the 

summer as a source (Schnoebelen and others, 2003). The larger 

concentration of atrazine in samples on the left bank of the river 

would correlate to intense agricultural use of the Big Sioux 

River basin, and might possibly delineate a separation of 

streamflow between the Missouri and Big Sioux Rivers. Acetochlor, alachlor, metolachlor, promenton, and trifluralin were 

detected in several samples but at extremely low concentrations. Carbofuran was detected at estimated concentrations in 

the June 25, 2003, sample on both sides of the river; this would 

follow the pattern observed in previous studies that large carbofuran concentrations occur in the month of June (Schnoebelen 

and others, 2003). Carbofuran is a pesticide that is applied in the 

summer months for agricultural insect control.

Table 4. Selected dissolved pesticides in samples from Missouri River at Sioux City, Iowa, 2002-2003.

[All data in micrograms per liter. M/D/YY, month/day/year; E, estimated value; N, presumptive evidence of presence; T, below the long-term method detection 

limit, MDL; <, less than]

Date

(M/D/YY) Time Acetochlor Alachlor Atrazine Carbofuran Deethylatrazine

Metolachlor Promenton Trifluralin

Left bank (Iowa)

12/3/2002 15:10 <0.006 <0.005 0.018 <0.020 E 0.007 E,T 0.002 E,T 0.005 <0.009

3/19/2003 11:25 0.023 <0.005 0.051 <0.020 E 0.020 0.157 <0.015 <0.009

6/25/2003 11:45 0.439 0.022 2.11 E 0.014 E 0.088 0.283 E,N 0.013 <0.009

Right bank (Nebraska)

12/3/2002 14:50 <0.006 0.005 0.017 <0.020 0.006 0.001 E,T 0.004 <0.009

3/19/2003 11:55 <0.006 <0.005 0.017 <0.020 E 0.009 0.014 <0.015 <0.009

6/25/2003 12:50 0.657 0.029 1.22 E 0.027 E 0.076 0.248 E,N 0.076 E,N 0.007
Summary 13

Table 5. Pesticide constituents not detected in surface-water samples from Missouri River at Sioux City, Iowa, 2002-2003.

[μg/L, micrograms per liter]

Constituent

Method

detection

limit

(μg/L)

Constituent

Method

detection

limit

(μg/L)

Constituent

Method

detection

limit

(μg/L)

Alpha-HCH 0.046 Ethlfluralin 0.009 p.p’-DDE 0.0025

2,6-Diethylanline 0.006 Ethoprophos 0.005 Parathion 0.010

Azinphos-mthyl 0.050 Desulfinyfipronil amide 0.009 Pebulate 0.0041

Benfluralin 0.010 Fipronil sulfide 0.005 Pendimethalin 0.022

Butylate 0.002 Fipronil sulfone 0.005 Phorate 0.011

Carbaryl 0.041 Desulfinyfipronil 0.004 Propyzamide 0.0041

Chlorpyrifos 0.005 Fipronil 0.007 Propachlor 0.010

Cis-Permethrin 0.006 Fonofos 0.100 Propanil 0.011

Cyanizine 0.018 Lindane 0.004 Propargite 0.023

Dacthal 0.003 Linuron 0.035 Simazine 0.005

Diazinon 0.005 Malathion 0.027 Tebuthiuron 0.016

Diazinon-d10 0.100 Parathion-methyl 0.006 Terbacil 0.034

Dieldrin 0.0048 Metribuzin 0.006 Terbufos 0.017

Disulfoton 0.021 Molinate 0.0016 Thiobencarb 0.0048

EPTC 0.002 Napropamide 0.007 Tri-allate 0.0023

Summary

The City of Sioux City, Iowa obtains part of its municipal 

water supply from the Missouri River alluvial aquifer. The U.S. 

Geological Survey, in cooperation with City of Sioux City, conducted a study to provide information about the riverbed elevation and water quality of the Missouri River at Sioux City.

The alluvial aquifer along the Missouri River at Sioux City 

consists of sand and gravel deposits of glacial and fluvial origin. 

The Missouri River riverbed consists predominately of sand 

and gravel throughout the study area. The thickness of sediments overlying the municipal collector-well laterals are of 

concern for the filtration of drinking water being obtained by 

Sioux City. A consistent thickness of 20 to 30 ft of sediment 

overlies the collector-well laterals to provide a filter for the 

water supply. The cross-section data show scour and fill over 

the period from October 1, 2002, to September 30, 2003, but a 

thickness of 20 to 30 ft of sediment overlying the laterals was 

maintained. These changes appear to coincide with rising and 

lowering Missouri River discharge that is controlled by the U.S. 

Army Corps of Engineer’s Gavins Point Dam upstream from 

the study location. 

Results of water-quality analyses of the Missouri River 

were similar across the width of the river. However, somewhat 

higher concentrations of chloride, ammonia nitrogen, nitrite 

plus nitrate nitrogen, deethylatrazine, and atrazine were 

detected along the left bank (Iowa side) of the Missouri River 

compared to the right bank (Nebraska side). The left bank is the 

side of the Missouri River where the Big Sioux River enters 

upstream from the sampling cross section. Water-quality results 

indicate that water from the two rivers is not well mixed and that 

water from the Big Sioux River potentially has a greater influence on water quality at the municipal well field than does the 

Missouri River. Therefore, understanding the water quality of 

the Big Sioux River may be crucial to understand variations in 

water quality at the municipal well field and to protect the 

supply source.
14 Riverbed Elevations and Water Quality of the Missouri River at Sioux City, Iowa, 2002-03

References

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Prepared by the Iowa District office:

U.S. Geological Survey, WRD

Room 269, Federal Building

P.O. Box 1230

400 South Clinton Street

Iowa City, IA 52244

Text layout by Ella M. Decker, USGS, Huron, South Dakota.

Graphics layout by Connie J. Ross, USGS, Huron, South Dakota.

Information regarding the water resources in Iowa is available at URL

 http://ia.water.usgs.gov/

This publication is available online at URL

 http://pubs.water.usgs.gov/sir20045079
Christiansen—Riverbed Elevations and Water Quality of the Missouri River at Sioux City, Iowa, 2002-03—SIR 2004-5079

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